Leaking roof (under water heater vent pipe)

[CCCA]

We had a big rainstorm last night and hear some dripping in our laundry/utility room.  The leak appears to be under the roof penetration for the gas tankless water heater.  I took a picture from the top of the ladder to check it out.  unfortunately it's a 2 story house with a moderately steep roof angle (so super scary to go on the roof).   

Anyway, here's a picture of the water heater vent pipe.  I've highlighted something that I think might be the cause of the leak.  The rusty cone on the bottom looks like it slips over the galvanized collar above it.  The two white sealant stripes seems to me that there should only be one (originally there to seal the collar to the pipe above), but somehow over time the two parts separated and water can get in between.  Does that make sense?  I'm not that familiar with the vent roof flashing for the gas vents.

We didn't have a ton of water.  I put a 5 gallon bucket below the leak and only got maybe a 1/8-1/4 inch of water.  so it seems reasonable that the issue is relatively small.  Do you think replacing all the flashing is necessary or just resealing that seam?

I suppose it's also possible that the leak is also above that on the other area with white sealant/caulk where the pipe diameter changes.

[lthenderson]

The gap between the two stripes of sealant doesn't look even like they connected together in the past. I'm guessing it has always been like that. If you can't find any new cracks in the sealant where water might be getting in, the other place I would look is between the rows of shingles downslope of where the pipe protrudes through the roof. If it was properly flashed, if you carefully lift up the shingle below, you should see a metal flange between the two layers of shingles. Any water that goes between the metal cone and the shingle above should come out on top of this flange for the rest of its journey down the roof. If you can't see the flange, then that means the water then travels between your roof sheathing and shingles all the way to the first available hole to infiltrate  your house. The shingles may have sealed to the flange for awhile to prevent this but now that seal has gone and water is finding its way inside. I see this all the time when people get their roofs reshingled and contractors are too lazy to redo the flanges properly.

If you find that it isn't flashed correctly, you can reshingle that area to do it correctly or apply roofing tar to that joint to prevent water from getting under the shingles. It will have to reapplied periodically every couple years until the rest of the roof needs reshingled anyway.

[zolotiyeruki]

It looks to me like the vent pipe moved (or was moved) some time after installation.  I'd say reseal the seam, then spray the hole thing heavily with a garden hose and see if anything drips through :)

[paddedhat]

It looks like a mess involving the installation of a "B-vent" gas flue, through an existing stove pipe. The white caulk was probably an attempt to solve the problem previously. It also appears, and I certainly could be wrong, that the B vent is installed upside down, since the flange is arranged that it would appear to collect water. Look up B-vent, download an installation manual and try to determine how badly that whole mess has been kludged together. If it's reasonably safe, the addition of two storm collars, one above the first caulked up mess, and another above the second, should eliminate the leak.

[zolotiyeruki]

It looks like a mess involving the installation of a "B-vent" gas flue, through an existing stove pipe. The white caulk was probably an attempt to solve the problem previously. It also appears, and I certainly could be wrong, that the B vent is installed upside down, since the flange is arranged that it would appear to collect water. Look up B-vent, download an installation manual and try to determine how badly that whole mess has been kludged together. If it's reasonably safe, the addition of two storm collars, one above the first caulked up mess, and another above the second, should eliminate the leak.

Wow, I didn't even bother looking at the top of that stack.

If it were my house, I get a new boot, pull out the old one, and get it all installed properly, so you never have to worry about it again.

[paddedhat]

It looks like a mess involving the installation of a "B-vent" gas flue, through an existing stove pipe. The white caulk was probably an attempt to solve the problem previously. It also appears, and I certainly could be wrong, that the B vent is installed upside down, since the flange is arranged that it would appear to collect water. Look up B-vent, download an installation manual and try to determine how badly that whole mess has been kludged together. If it's reasonably safe, the addition of two storm collars, one above the first caulked up mess, and another above the second, should eliminate the leak.

Wow, I didn't even bother looking at the top of that stack.

If it were my house, I get a new boot, pull out the old one, and get it all installed properly, so you never have to worry about it again.

I doubt that the boot is leaking at all. The retrofitted B-vent is such a cluster-F, I would be shocked if the problem isn't located at the "ledge" where the B-vent was shoved up through an old piece of "zero-clearance" chimney pipe, left over from an old fireplace, or wood stove installation.  If it was my house, I would start again, get the proper materials, install the correct roof flashing, and reinstall the B-vent so it is done according to manufacturer's instructions. I also wouldn't spend a night in that place without a working CO detector. If the gas vent is that cobbled together, the whole installation is IMHO, suspect at best.

[CCCA]

I finally got onto the roof today to fix the issue.  Upon close inspection the two places in the original picture that had white caulk were areas that water could enter as the caulk was dry and peeling and gaps had formed.  The two red lines I indicated were, in fact, an area where the caulk had separated.  Also above that, the caulk on the little flat lip had separated a bit away from the b-vent pipe.  I pulled off the old caulk and resealed it.  I also put on a new storm collar over that top caulked area just to keep water from sitting on top of the little lip.  It was my first time on the roof (it's high!) and doing any sort of vent/flashing/roof related repairs.   I'll see how it fares in the next rain, which is supposed to come tomorrow, but I think I fixed all of the glaring issues. 


The vent itself seems fine and I do have a CO meter in the utility room.


thanks for all the advice and insights into the issues.

[paddedhat]

I finally got onto the roof today to fix the issue.  Upon close inspection the two places in the original picture that had white caulk were areas that water could enter as the caulk was dry and peeling and gaps had formed.  The two red lines I indicated were, in fact, an area where the caulk had separated.  Also above that, the caulk on the little flat lip had separated a bit away from the b-vent pipe.  I pulled off the old caulk and resealed it.  I also put on a new storm collar over that top caulked area just to keep water from sitting on top of the little lip.  It was my first time on the roof (it's high!) and doing any sort of vent/flashing/roof related repairs.   I'll see how it fares in the next rain, which is supposed to come tomorrow, but I think I fixed all of the glaring issues. 


The vent itself seems fine and I do have a CO meter in the utility room.


thanks for all the advice and insights into the issues.

Good job. Just a guess, but I think that the new collar will probably eliminate the issue.